First order of business is getting a bug catching addon (Swatter or BugSack/BugGrabber) if you don't have one, or enabling "Show Lua errors" from Game Options -> Help.

It's possible you're getting spammed by errors you're not seeing.

If that's the case, the author will have something to work with.

If you already have one of the above and not getting any Lua errors, then you need to provide more info.
Does this happen in all areas? The more info the better.

Dridzt; I turned on the 'Show LUA Errors' feature but no indication of errors. Where would I see these? Also, this does occur in all areas I've been in this far today; Stormwind and Panderia. I"ll update as more locations are visited.

i'm having a similar problem of getting reduced to either 0 or 1 fps, but only when i open the character info screen, and so far, no other time (just laggy otherwise) although i don't remember seeing anything having to do with any add-on (other than built in from blizz) in my bugsack, but it's happening consistently, and makes it difficult to swap out gear when i get something new. i'm forced to right click on an item in my bag to equip and just try to remember what i have, as going into character info to get equipment manager to save is horrendous...it sticks forever i updated my nvidia card driver the other day, and at first i thought it had helped, but it seemed temporary...the reboot prob cleared whatever is causing the massive lag/standstill, but it comes back anyway. i still have the usual amount of available memory, so for now, i assume there is some conflict with a recently updated add-on that i haven't had time to isolate yet. if i come across any lua errors, i will post more info...

i'm having a similar problem of getting reduced to either 0 or 1 fps, but only when i open the character info screen, and so far, no other time (just laggy otherwise) although i don't remember seeing anything having to do with any add-on (other than built in from blizz) in my bugsack, but it's happening consistently, and makes it difficult to swap out gear when i get something new. i'm forced to right click on an item in my bag to equip and just try to remember what i have, as going into character info to get equipment manager to save is horrendous...it sticks forever i updated my nvidia card driver the other day, and at first i thought it had helped, but it seemed temporary...the reboot prob cleared whatever is causing the massive lag/standstill, but it comes back anyway. i still have the usual amount of available memory, so for now, i assume there is some conflict with a recently updated add-on that i haven't had time to isolate yet. if i come across any lua errors, i will post more info...

I was having the same problem when opening my character screen and came to find out it was an addon named playerscore/gearscore and once I shut it down i have'nt had the problem since.